There are lots of advantages to using a CSV and a small tank on a low producing well. An 80 gallon size tank holds about 25 gallons of water. Your pump and well see this as an additional load to supply after you have turned off all the faucets. Many times the well will be pumped dry before the pressure tank is refilled. A 1.5HP pump from 210’ should produce about 14 GPM. Every time this pump comes on it is pumping 14 GPM until the pressure tank is full. If your well doesn’t make 14 GPM, it will quickly pump the well dry even when just refilling the tank.
A CSV will turn that pump into a variable flow pump and will let it draw from 1 GPM to 14 GPM matching the amount of water you are using. If you are only using a 3 GPM shower, the CSV only lets the pump draw 3 GPM from the well. If you know your well has a recovery rate of say 6 GPM, then just never run more than 6 GPM when watering the yard, and you will not pump the well dry or cycle the pump to death.
Also when you turn off all the faucets, the CSV only lets the tank refill at a rate of 1 GPM, so you won’t pump the well dry while refilling the tank. However, if you use a large tank, the first ¾ of the tank will be refilled at 14 GPM until the CSV starts to work and tops off the last ¼ of the tank at 1 GPM. So again a big tank is just an extra load on an already low producing well.
I would use a CSV1A with a 4.5 gallon size tank and a Cycle Sensor to protect from a dry run. The pumptec will not work with a CSV, as it sees the low amps caused by the CSV as a dry well condition and shuts the pump off when it should not. The Cycle Sensor is infinitely adjustable and can easily be set to know the difference between the low amps caused by a CSV and the slightly lower amps seen when the well pumps dry.
I have a well that only produces 1 GPM. But there is about 100 gallons stored in the well before it pumps dry. I have a 10 GPM pump, a 4.5 gallon size tank, and a Cycle Sensor. I can use 10 GPM for 10 minutes or 5 GPM for 20 minutes before the well is pumped down. As long as I shut off the faucets before this happens, the CSV slowly refills the little tank at 1 GPM and the pump shuts off without pumping the well dry. Only when I have a lot of company do I have a chance of the well pumping dry and the water shutting off. But if it does my Cycle Sensor is set to restart the pump after 10 minutes. If my well would recover faster than 1 GPM, I could set it to restart in a couple of minutes or so.